Field of the Invention
The present invention relates generally to a device for enlarging and projecting a microfilm image, which is adapted for use in reader, reader printer, enlarger or enlarged image printer for picking up said microfilm image. More particularluy, it pertains to such a device by which the magnification of enlargement of the image may be changed and the projected and enlarged image may be rotated.
Related Art of the Invention
Various types of reproducers for enlarging an image born by a microfilm, such a image being referred to as microfilm image throughout this specification and appended claims, have hitherto been known in the art. The known devices include a reader for displaying an enlarged microfilm image on a display screen, a reader printer for delivering an enlarged image, which as been once projected on the reader, to a printer to produce a hard copy of the image, and various other types of enlargers and printers for printing enlarged images. In such a device, it becomes frequently necessary that the magnification of enlargement of the image should be varied or the enlarged image should be rotated as required.
For the aforementioned purposes, a magnification varying optical system and an image rotating optical system are individually disposed at separate locations in the light path from the microfilm and the projection lens. In other words, the magnification varying optical system includes a mirrors or reflectors disposed intermediately of the light path so that they may be moved without changing the angular disposition and the movements thereof are interrelated with the movement of the projection lens. On the other hand, the image rotating optical system is constituted by a triangular prism for receiving a light from one end face, so that the received light is totally reflected inside of the prism at odd occations to go out of the prism through another end face of the prism. The image is rotated by rotating the prism about the optical axis.
However, since the conventional device has a magnification varying optical system and an image rotating optial system individually mounted at different positions, as described above, there are the problems that the device has larger dimensions and the number of parts necessary for assembling the device is increased.
Another disadvantage is that it is impossible to allow the incident light to transmit fully (at a percent transmission of 100%) through both end faces, i.e. the incident face and the face through which the light is emitted, of the prism used for rotation of the image, leading to the detriment that the quality of the enlarged image is degraded.